Originally Posted by TORQUERULES
Oil can get into the intake from two sources. 1. The valve cover/cam cover breather system which I have just separated from the air intake and the PCV system which I am using h catch can for.
Most of it is from the PCV system, but the valve cover/cam cover breather gets some too.
The breather tube for the valve cover is mostly an emissions control system. Old engines, and racing engines, use an open breather here (many did not/do not even use a PCV system---on my Mustang I use a vacuum pump). The EPA does not want oil fumes into the air. Thus the tube I eliminated.
My buddy put a oil separator from the valve cover to intake air line and had not one drop of oil. It is possible oil vapors are far less. The main area is from the crankcase behind the manifold. James Baron Racing has detailed pictures of this.